handle tree overflow in count(distinct)

test heap table/tree overflow in count(distinct)


mysql-test/r/count_distinct2.result:
  added test for tree/heap table overflow
mysql-test/t/count_distinct2.test:
  test tree/heap table overflow
sql/item_sum.cc:
  handle tree overflow in count(distinct)
sql/item_sum.h:
  t

1 files changed, 14 insertions, 3 deletions

diff --git a/sql/item_sum.h b/sql/item_sum.h
index 863623c3b1a..1aa7f78d786 100644
--- a/sql/item_sum.h
+++ b/sql/item_sum.h
@@ -148,15 +148,26 @@ class Item_sum_count_distinct :public Item_sum_int
   bool fix_fields(THD *thd,TABLE_LIST *tables);
   TMP_TABLE_PARAM *tmp_table_param;
   TREE tree;
-  bool use_tree; // If there are no blobs, we can use a tree, which
+  uint max_elements_in_tree;
+  // calculated based on max_heap_table_size. If reached,
+  // walk the tree and dump it into MyISAM table
+  
+  bool use_tree;
+  // If there are no blobs, we can use a tree, which
   // is faster than heap table. In that case, we still use the table
   // to help get things set up, but we insert nothing in it
-  int rec_offset; // the first few bytes of record ( at least one)
+  
+  int rec_offset;
+  // the first few bytes of record ( at least one)
   // are just markers for deleted and NULLs. We want to skip them since
   // they will just bloat the tree without providing any valuable info
 
-  friend int composite_key_cmp(void* arg, byte* key1, byte* key2);
+  int tree_to_myisam();
   
+  friend int composite_key_cmp(void* arg, byte* key1, byte* key2);
+  friend int dump_leaf(byte* key, uint32 count __attribute__((unused)),
+		Item_sum_count_distinct* item);
+
   public:
   Item_sum_count_distinct(List<Item> &list)
     :Item_sum_int(list),table(0),used_table_cache(~(table_map) 0),